Batteries and Charging/Stacking Question

[uzzaperez]

I'm using protected batteries - Ultrafire 3.6 volt Li-ion 163040/CR123s.

1. I just got a new charger. I've been charging on a universal 3.7 volt charger. I got a new Ultrafire 3.6 volt charger. Should I have any concerns moving used batteries to a different charger?

2. I've been using them in a single battery 3.7 volt device. Now I want to stack them in a two battery device. Should I have concerns stacking used batteries that haven't been stacked before? Also, should I have concerns stacking used batteries with new batteries - do I need to keep them straight which is which and always use the same two batteries when stacking?

3. What about using the batteries interchangeably with another device, say a flashlight that uses the same batteries?

Gracias for any feedback.

 

[Gas]

I don't think so. The important thing is just not to use batteries with different voltages. Even if a battery is newer than another they should both supply almost the same energy so if one provides a bit less nothing bad is going to happen.

 

[candre23]

You're fine on all counts. Whether the charger says 3.6V or 3.7V, it's actually charging to 4.2V. Li-ion batteries take a 4.2V charge, but drop almost imeadiately to about 3.8V, then drop very slowly to about 3.5V before they're considered "empty" and the protection circuit cuts them off. Stacking won't be a problem, but if you're going to stack, you should swap the order after every charge just to make sure they wear evenly. Mark the batteries and if you have them stacked A-B one time, they should be B-A the next time. It's not absolutely vital, but you will prolong the overall life of the set if you do this.

 

[Quick1]

What Candre23 said. and if they're protected you don't have any concerns. It's just a matter of getting better performance out of them and extending their usable life.

For example, stacking them in a different order each time.
When you stack batteries the whole stack performs to the extent of the "weakest" unit. It seems there is some effect where the top (pos?) end of the stack gets depleted more than the neg end. When that battery discharges to the low voltage threshold of the protection unit then your PV cuts off. When you throw the batteries into your charger that battery will be depleted more than the other one.
a) your battery charger only has a single circuit. When one of the cells gets charged all the way (that would be what was the bottom one on the stack) the charger cuts off and the other battery isn't fully charged. Back into the PV, repeat, etc.
b) your battery charger does have independent circuits. Both batteries get fully charged again. The battery that was a little more depleted takes a bit more charging. Your batteries only have a finite amount of discharge/recharge cycles. Actually it's not discrete cycles but amount of discharge/recharge. It doesn't matter how many times you put them on the charger, it only matters how much current (cumulative) you take out and put back. So if the top battery is always getting discharged and recharged a bit more than the other it will hit the end of it's usable life sooner than the other one. They don't just die all of a sudden. They gradually have less capacity. So the performance of the pair degrades faster because one of the batteries is always getting used more than the other but the stack performs only as well as the "weakest" one.

In any event, with protected batteries there shouldn't be much of anything you could do to cause a catastrophic failure or damage. It's just that you might not get all you can out of them.

 

[uzzaperez]

Gracias Gents.

 

[5thelephant]

This is very good information. Thank you.